Sharks as Predators of Humans

According to researchers, sharks are only dangerous when you're injured or
"mistaken" for food. I've also heard that the Tiger shark is one of
the few animals which actually consider a healthy human as prey and will stalk
and hunt you down, then eat you completely. Is this true and, if so, are there
other animals that behave this way?

Greg in Sudbury, Ont.

Interesting meta-question, Greg!

Firstly, allow me to put the danger posed by sharks in perspective.
World-wide, of the countless hundreds of millions of people who work and play in
the sea each year, only 70 to 100 are bitten by sharks and only 10 or so are
killed. In contrast, many thousands drown each and every year. The sea itself is
*far* more dangerous than any shark.

That said, it is NOT true that sharks are only dangerous when one is injured
or mistaken for food. In fact, the vast majority (something on the order of 96%)
of shark 'attacks' are single strikes — often either a bump with the snout or a
raking with the upper jaw teeth only, with no biting or removal of tissue. This
fact *strongly* suggests that most shark attacks have little — if anything —
to do with feeding. It is my suspicion that the two main motivations of shark
attacks are: 1) self-defense and, 2) investigation. Let's look at each of these
in turn.

Like any wild animal, sharks will defend themselves if threatened. Despite
their reputation for ferocity, sharks are actually remarkably non-violent
creatures. If a shark 'feels' threatened — due to being pursued, grabbed,
speared, or otherwise molested — it will most likely either swim away or
attempt to signal its unease by way of a specific display, a kind of 'body
language'. My own field research has revealed that the exact character of shark
displays elicited in conflict situations varies from species to species, but
there are some features common to all species studied to date. Among the most
obvious of these is a pronounced lowering of the pectoral fins, the paired,
wing-like fins located behind the gill slits. If this warning is ignored, the
shark may swim away rapidly or launch a lightning fast, slashing attack. Since
we are the visitors in the sharks' living room, the onus is on us to be a
well-behaved guest, to recognize their signals, and to respond appropriately.

Like any opportunistic predator accustomed to feeding on broad spectrum of
prey types, sharks must be perennially ready to investigate new potential food
sources. despite their reputation for stupidity, sharks have remarkably large,
complex brains, complex and subtle social behaviors, a well-developed sense of
curiosity, and exhibit a rudimentary ability to reason. Without benefit of
hands, sharks investigate novel objects in their environment with their mouths.
Many sharks can control their jaws with astonishing dexterity, and their teeth
and gums are highly sensitive. There are many well-documented reports of sharks
gently mouthing objects in the sea. Given that shark jaws are incredibly
powerful and their teeth extremely sharp, it is clear that sharks are capable of
inflicting much more serious wounds on humans than they usually do. It is my
suspicion that to most sharks, a human being is a large, unfamiliar, and
altogether frightening creature. But some of the larger species, such as the
Great White (Carcharodon carcharias) have learned that they have little to
fear in their liquid realm and may be willing to take a gentle test nip. In many
cases, the victim is released after a single contact and suffers only minor
wounds. It seems more likely that such 'attacks' are motivated by curiosity
rather than predation.

Human beings are NOT a regular part of the diet of any species of shark, and
very, very few people have ever been consumed by their attacker. (Feeding on
human corpses is another matter, of course — any carnivore will scavenge when
the opportunity arises, and we are not exempt from this practice). Not even the
fearsome Great White Shark — large individuals of which regularly catch and
consume marine mammals — shows any particular interest in killing or eating a
human being. After all, if a swift, 2,000-kilogram (4,400-pound) Great White
with razor-sharp, serrated teeth wanted to eat a human, there is very probably
*nothing* that a comparatively slow-swimming, 100-kilogram (220-pound), unarmed
primate could do to prevent it.

So the real question isn't 'Why do sharks sometimes attack humans?'. The
question is: why don't they do it far more often?

Cheers,

— R. Aidan Martin

Important New Book on
Shark Attacks!

The culmination
of four decades' of research by my friend and colleague Ralph Collier,
President of the
Shark Research Committee, this book is the first scientific
study of every verified shark attack that occurred along the
Pacific Coast of North America during the 20th Century. Vivid
accounts of attacks by survivors, rescuers, and witnesses are punctuated
with chilling, never-before published photos. Patterns in shark
attacks are identified, possible motivations for attacks are discussed,
and activity-specific safety guidelines for swimmers, divers, surfers,
and sea kayakers are offered. The individual case histories are
fascinating; the general conclusions and safety guidelines are
applicable word-wide. If you are interested in Great Whites or
shark attacks, this is a Must Have book.